Arc-melting furnaces



June 1l, 1957 J. PRESTON ET Al..

ARC-MELTING FURNACES Filed Sept. 28, 1955 F/GJ.

' /NvE/vro/zs 'fw/G. 2. './Acx PRESTO/v FRANC/s w/LL/AM B/G/VELL ArcHEsO/v United States Patent O ARC-MELTIN G FURNACES .lack Preston, Summit, N. J., and Francis William Bignell Atcheson, Sutton Coldtield, England, assignors to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain Application September 28, 1955, Serial No. 537,176

Claims priority, application Great Britain June 15, 1955 2 Claims. (Cl. 13-33) This invention relates to improvements in arc melting furnaces particularly those employed for melting metals and alloys which have high melting points and are reactive such as titanium, zirconium and tantalum.

In arc melting furnaces for such metals the metal is continuously fed into and is melted in a water-cooled metal crucible which is sealed by a cover through which pass one or more electrodes, an arc or arcs being struck between the metal in the crucible and the electrode tip or tips. Contamination of the molten metal by oxygen and nitrogen in the air must be avoided and consequently the crucible is customarily either evacuated or filled with an inert gas. The metal is introduced into the crucible in the form of pellets or granules and in order to maintain a continuous feed of unmelted material it is usual practice to provide a feed inlet in the cover of the crucible so positioned as to direct the material into the molten pool in the crucible. Such furnaces are hereinafter referred to as furnaces of the kind described.

The present invention comprises an arc melting furnace of the kind described comprising a feed deflector plate disposed in the upper zone of the furnace between the feed inlet and the electrode or electrodes to deflect the falling stream of feed metal away from the electrode.

A difficulty encountered hitherto in furnaces of the kind described has been due to the lack of control of direction of the falling stream of pelleted or granular material after leaving the feed inlet. The uncontrolled stream of material spreads during its fall and tends to impinge on the electrode, directly or after iirst impinging on the crucible walls and being deflected thereby. Pieces of unmelted material, particularly those in a more or less nely divided state, thus striking the hot electrode tip are prone to adhere to it and these adhering pieces may build up to such an amount that there is a risk of causing an electrical short circuit between the electrode and the crucible. Our invention obviates or minimises the possibility of the feed material striking the electrode tip, and also has the advantage of extreme simplicity of construction.

An arc melting furnace for the melting of titanium in accordance with one embodiment of the invention is de- 2,795,636 Patented June 11, 1957 'ice scribed by way of example, with reference to the accompanying drawings, in which:

Figure 1 is an elevational view in section of the part of the furnace.

Figure 2 is a section along the line A--A of Figure 1.

Referring to the drawings, the furnace comprises generally a crucible 1 and a cover part 2 through which pass three electrodes 3 and a tubular feed inlet 4. A detachable ring 6 is located between the crucible and the cover part in a groove provided in the upper edge of the crucible.

A deflector plate 5 consisting of a segment of a cylinder made from steel or other suitable material is mounted on brackets 7 projecting inwardly from the ring 6 and is disposed in the upper portion of the crucible and coaxially therewith between the feed inlet and the nearest electrode. The deflector plate is located sufficiently far away from the electrode to prevent arcing between the electrode and the plate. The distance between the plate and the crucible wall is suicient to permit easy passage of the granular or pelleted material between the two.

The upper edge of the deflector plate is above the lower end of the feed inlet and the plate extends downwardly into the crucible to a depth limited by the height which the completed ingot will attain. The width of the plate is greater than that of the feed inlet being adequate to shield all three electrodes from material falling either directly from the feed inlet or after deection from the wall.

We claim:

1. An arc melting furnace comprising a crucible having an open top, a cover closing said top, at least two spaced inlets adjacent the top of the furnace for electrode means and for feed metal, an annular member, means for detachably mounting said member between said cover and the top of said crucible, and a dellector connected to said annular member and extending into the crucible adjacent the top thereof, at least a portion of said deector being disposed intermediate said spaced inlet means.

2. The structure defined in claim 1 wherein the feed metal inlet includes a tube extending through the cover, and said deflector being in the form of an arcuate plate extending above the bottom of said tube.

References Cited in the le of this patent UNITED STATES PATENTS 750,753 Contardo Ian. 26, 1904 941,768 Diefenbach et al Nov. 30, 1909 1,192,050 Fleming July 25, 1916 1,463,970 Pope Aug. 7, 1923 2,541,764 Herres et al. Feb. 13, 1951 2,592,517 Ingelsrud Apr. 8, 1952 2,738,373 Alexander Mar. 13, 1956 

